Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

38-15 Project
#16

...or, maybe, a previous owner ran the set with old electrolytics to the point that it began to seriously overload the transformer windings. A bad or marginal transformer does not always manifest itself with leaking wax.

Don't overlook that possibility, when/if all else fails.

--
Ron Ramirez
Ferdinand IN
#17

I powered the set off my variac last night on 110v and after about 20-30 minutes the PT was at 113 degrees. I didnt get a chance to check for carbon traces on the band switch or the tube sockets yet maybe tonight.

I hope it's not a PT issue. It ohmed out fine when I first started this project.

Would it be worth it to unhook the secondaries of the PT and see if it still gets hot with no load?

-Keith
#18

ipwizard Wrote:Would it be worth it to unhook the secondaries of the PT and see if it still gets hot with no load?

Yes!

--
Ron Ramirez
Ferdinand IN
#19

You can always pull all the tubes which will eliminate any load on the transformer. Should not get hot then.

But 113 F is not indicative of any major problem. You can insert a bucking transformer to get down to 110 volts, and that would be a good thing. Check the output stage once again to see if bias is correct and/or sub another output tube.

A good old fashioned DD C ma meter can be inserted anywhere along the voltage divider to measure current draw. I have several different ones, 50ma, 250 ma, 1 amp. Red dot goes to the more positive side.
#20

I had a Marine radio tech tell me that the most dangerous thing out there was a Marine Grunt with a screwdriver.
#21

Dang ip, these guys think 113 is hot! Ambient here at my house was 103 today.

John
Las Vegas, NV USA
#22

lol It was 101 here in AZ today not too bad seems like it's cooling off now no more 115+ hopefully. Only 94 in my garage much more user friendly then the 107-110 it was a month ago.

Well I cleaned all the tube sockets again, and douched the bandswitch with deoxit. I ran it without any tubes or dial light and the PT never not hotter then 95 (it's 94 in the garage) so I think thats a good thing and it was plugged into the wall ~123-125vac. The amp meter I had in line showed .85mA being pulled.

I put the tubes and dial lamp back in and it is pulling 309mA (according to riders it should be pulling 40w, or 348mA) at 115vac running off my variac, and the PT is at 105 and its been running for about 15 minutes now. I'll leave it run awhile longer and see how it does.

I did notice that the 84 tube socket was pretty lose (tube pulled out real easy) so I tightened up the connectors. Also the DC from the cathode of the 84 (pin4) tube is low at 260vdc, schematic calls for 290vdc.

-Keith




Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
Philco 60 Squealing
I seem to remember eliminating a squeal by changing the IF frequency by a few KHz. Not that you should put too much tru...fenbach — 08:48 PM
Philco 42-390, code 121 speaker
These speakers pop up on eBay regularly, even if at bloated prices. Honestly, have not seen many parts on swapmeets.morzh — 08:38 PM
Philco 38-7 Speaker
The put-put is not like the speaker problem.morzh — 08:29 PM
Mission Bell Model 19A Car Radio
Hello everyone,  As mentioned in my last post I was going to see if the vibrator / rectifier section could be persuaded...Antipodal — 08:21 PM
Philco 60 Squealing
Wondering if I did it backwards. If a coil was wound backwards, the oscillator would not work at all. Old school...Chas — 07:23 PM
Philco 38-7 Speaker
4-ohm speaker. Black, Green leads.tludka — 07:00 PM
Philco 42-390, code 121 speaker
#87 on the schematic.  This radio had a 8" Zenith  speaker attached to it when I got it. I do don't know the hist...Stevelog — 06:39 PM
Philco 60 Squealing
I'm pretty sure I now have the litz wire soldered. This did not make any difference. Back in April I rewound the seconda...dconant — 06:25 PM
Philco 38-7 Speaker
Just to make sure, you chose either 4 ohm into 5K or into 10K? (blk-org or blk-grn)morzh — 06:23 PM
Philco 38-7 Speaker
I have let this one sit because of other duties. Now I am back, and I have a couple of questions. I hooked up a Hammond ...tludka — 05:34 PM

[-]
Who's Online
There are currently 4899 online users. [Complete List]
» 2 Member(s) | 4897 Guest(s)
AvatarAvatar

>